Methods

Data were obtained from National Health and Nutrition Examination Survey 2003–2004,
a cross-sectional observational study conducted by the National Center for Health
Statistics of the Centers for Disease Control that uses a stratified, multistage probability
design to obtain a nationally representative sample of the U.S. population. The analysis
included 402 healthy U.S. adults with valid accelerometer, cardiorespiratory fitness,
and fasting plasma glucose and insulin concentrations. After controlling for relevant
confounding variables we performed a multiple linear regression to predict homeostatic
model of insulin resistance (HOMA-IR) based on average daily minutes of moderate-to-vigorous
physical activity (MVPA).

Results

In our bivariate models, MVPA, cardiorespiratory fitness and body fat percentage were
all significantly correlated with log HOMA-IR. In the complete model including MVPA
and relevant confounding variables, there were strong and significant associations
between MVPA and log HOMA-IR (β= −0.1607, P=0.004). In contrast the association between
cardiorespiratory fitness and log HOMA-IR was not significant.

Conclusion

When using an objective measure of physical activity the amount of time engaged in
daily physical activity was associated with lower insulin resistance, whereas higher
cardiorespiratory fitness was not. These results suggest that the amount of time engaged
in physical activity may be an important determinant for improving glucose metabolism.